Cellular communication networks evolve towards higher data rates, improved capacity and improved coverage. In the 3rd Generation Partnership Project (3GPP) standardization body, several technologies have been and are also currently being developed.
LTE (Long Term Evolution) is a recently standardised technology. It uses an access technology based on OFDM (Orthogonal Frequency Division Multiplexing) for the downlink (DL) and Single Carrier FDMA (SC-FDMA) for the uplink (UL). The resource allocation to wireless devices on both DL and UL is performed adaptively using the concept of fast scheduling, taking into account the instantaneous traffic pattern and radio propagation characteristics of each wireless device. Assigning resources in both DL and UL is performed in the scheduler situated in a radio network node such as the radio base station.
In LTE Rel-11, a new downlink control channel, EPDCCH (Enhanced Physical Downlink Control Channel), was added to the standard. This channel can be used to transmit wireless device specific scheduling assignments for wireless devices that are EPDCCH capable. The EPDCCH channel is multiplexed with the physical downlink shared channel, PDSCH, in the shared data region. There are several use cases for EPDCCH such as increased control channel capacity, control channel ICIC (Inter-Cell Interference Coordination) support for HetNet and Combined Cell, and control channel beamforming.
Since PDSCH and EPDCCH are multiplexed in the same shared region, it is a great challenge to find a suitable balance of resource usage between PDSCH and EPDCCH.